First, the technical bit:
Both McAfee and Norton have a reputation for being 'resource hungry' (i.e. they can slow your computer down). They are no better (and, in many ways, far worse) than the free programs which are available. The majority of the 'regulars', here in AB's Technology section, use Zone Alarm Free edition (as their firewall) and AVG 7.5 Free (as their anti-virus solution). They top these up with free software, such as Ad-Aware SE Personal and/or Spybot Search & Destroy to provide anti-spyware provision. If you require the relevant links, just ask.
Now the financial bit:
McAfee can't have taken money from your account without some form of authorisation. If you set up a standing order, then there's nothing you can do about it because it was up to you to cancel the order. However, it's far more likely that the money was taken by direct debit. The rules of the direct debit scheme require that anyone who is about to take money from your account must notify you in advance. (The usual time lag is 10 working days, which is effectively a fortnight).
If the rules of the direct debit scheme are not adhered to, there is a guarantee that your bank is obliged to refund the money to you. So, assuming that the money was taken by direct debit, you should
contact your bank and demand that they refund the unauthorised withdrawal:
http://www.bacs.co.uk/BPSL/directdebit/general public/yourrights/
Chris